So I wanted something small to shoot paintball size projectiles and to be manualy powered. I used T piece brass piston valve (common design), shortened shrader valve for trigger, and smallest bike pump i could find for power source. The rest are brass fittings, teflon tape, epoxy glue and PP pipe for barrel. Need to improve tightness and smoothness oof piston operation and will be able to shoot some 15 yards relatively straight with about 3bar pressure.